rhm

Ah, well, I think I can address that. The reason I would convert a 700c bike into a 650b bike would be to convert a racing bike to a randonneuring bike. That works quite nicely, since you get the appropriate geometry for road riding, the appropriate springiness in the frame, and fatter tires for less wear and tear on the body on long rides. A long ride is 1200 km in four days. There are two basic problems with converting an MTB to randonneuring bike: 1, geometry. The MTB is designed for a much higher BB so you can have longer cranks (most MTB's have 175's, don't they?) AND plenty of clearance. You can lower the BB a bit by using a shorter fork, which will also make the frame angles steeper and the top tube (effectively) longer. That may result in the perfect geometry for someone, but it didn't work for me. I rode a Univega MTB converted to rando bike for a few months, a few years ago, without changing the geometry at all; it was okay, but the ground was very far away. I had to get off the seat entirely at every stop. Not a big deal, but not how I usually ride. And 2, MTB's are overbuilt for randonneuring purposes. That's extra weight and extra rigidity, both of which will help beat up the rider on long rides.

At least, that's what I tell myself. Whether any of this actually matters enough to improve my ride, I don't know. A heavier rider than myself might do very well with an old MTB. My last conversion, in the spirit of full disclosure, was a 700c racing bike to 26" rando bike, a feat accomplished through Gugificazione.